Squatting is a very dynamic activity that involves working all of the muscles and joints of the lower extremity. The biomechanics of a squat are very important in order to avoid injury as well as utilizing the proper musculature.
Key things to be aware of when squatting:
Maintain neutral spine with slight lumbar extension; do not round back at the bottom of the squat
Don’t let your knees track inside of your feet or over your toes
If mobility allows, make sure you are reaching at least parallel
Allow for full hip extension at the top of a squat to maximize full glute activation
Heels remain on the ground at all times
In order to avoid low back injuries when performing a squat, be sure to keep a neutral spine and avoid allowing your pelvis to posteriorly tilt (causing lumbar flexion). This can cause compressive and shearing forces on the spine and potentially causing a herniation or damage to the spinal ligaments.
Many individuals allow their knees to fall inwards or forwards over the toes. Both of these situations risk injury to the knees. This is mainly because of weak glutes and needing to recruit other muscles for stabilization.
To perform a proper squat it is imperative to have coordination between your glutes, hamstrings and quadriceps. Weakness to any of these muscles can cause compensatory techniques such as weight shifting or medial collapse of the knees as well as not allowing full hip extension at the end of your squat.